S10 Crewcab High mount Brake light

[Crewcab]

I have a 2001 S10 Crewcab that I noticed my high mount brake light is out.
I attempted to remove the lens to get to the bulb and found it would not
come off. My chiltons manual says for the Crewcab you have to take it to the dealer to get it replaced. Dealer says about $8.00 for the bulb and $50.00 to put it in. The regular brake lights are working with no problems. Don't know how long its been out. I just removed a camper shell so its now visable again. Anyone replaced one of these before. I'm thinking you need to drop the headliner and replace it from inside the cab. Any help would be appreciated.